模拟校友即可

题库之前有一题类似,y总讲过

substr()截取生日的灵活运用

/**
判断校友是否到场, 然后判断校友到场人数

找出最老的校友,若没有校友,找最老的那一个

*/
#include <iostream>
#include <cstring>
#include <unordered_map>

using namespace std;

int main()
{
    int m, n;
    cin >> m;
    unordered_map<string,bool> ext;
    for(int i = 0; i < m; i++)
    {
        string s;
        cin >> s;
        ext[s] = true;
    }
    cin >> n;
    int cnt = 0;
    string max_stu = "99999999", max_all = "99999999", res, res_all;
    for(int i = 0; i < n; i++)
    {
        string s, str;
        cin >> s;
        str = s.substr(6, 8);
        if (ext[s])
        {
            cnt++;
            if (str < max_stu) max_stu = str, res = s;
        }
        if (str < max_all) max_all = str, res_all = s;
    }
    printf("%d\n", cnt);
    if (!cnt) cout << res_all;
    else cout << res;
}

之前做的

#include <iostream>
#include <cstring>
#include <vector>
#include <unordered_map>
using namespace std;

unordered_map<string,bool> visit;

int main()
{
    int m, n;
    cin >> m;
    string str;
    bool flag = true, f1 = true;
    while (m --)
    {

        cin >> str;
        visit[str] = true;
    }
    cin >> n;
    vector<string> a;
    string id_all, id_ali, min, min_aln;
    while (n --)
    {
        cin >> str;
        string sstr = str.substr(6, 8);
        if (flag) min = sstr, flag = false, id_all = str;
        else{
            if (sstr < min) min = sstr, id_all = str;
        }
        if (visit[str])
        {
            a.push_back(sstr);
            if (f1) min_aln = sstr, f1 = false, id_ali = str;
            else
            {
                if (sstr < min_aln) min_aln = sstr, id_ali = str;
            }
        }
    }
    cout << a.size() << "\n";
    if (a.size() > 0) cout << id_ali;
    else cout << id_all;
}